EP 1 963 625 B1 discloses a generic camshaft having an outer shaft and an inner shaft arranged coaxially thereto, the inner shaft being supported directly against a stepless inner lateral face of the outer shaft by means of at least one securing device arranged on an axial end region of the shaft.
Owing to the necessary freedom of movement between the inner shaft and the outer shaft in an adjustable camshaft and/or owing to a necessary oil duct for a phase adjuster and/or bearing lubrication, a sufficient annular gap of between 0.2 and 2 mm in radial height is usually required between the inner shaft and the outer shaft. Sealing is therefore needed at the end of the two shafts to be able to build up the oil pressure necessary for the phase adjuster between the inner shaft and the outer shaft. With inner shafts known from the prior art, they are usually thickened in the region of a sealing ring, which can be achieved for example by removing material from almost the entire length of the inner shaft adjacent to the annular seal. This is however very expensive and requires an initially unmachined inner shaft with a comparatively large amount of material.